1.Field of the Invention
The present invention relates to an infrared irradiation lamp for an automobile which is mounted on an automobile and illuminates a forward portion of a vehicle with an infrared light, and more particularly to an infrared irradiation lamp for an automobile which has such a structure that an infrared light is formed by a globe for infrared light formation covering a bulb to be a light source and which is shared with a CCD camera having a sensitivity up to a near-infrared.
2.Description of the Related Art
For example, this kind of lamp has such a structure that a visible light source and a reflector are provided in a lamp housing formed by a lamp body and a front lens, an infrared light transmission globe having a surface coated with an infrared light transmission multilayer film is provided to cover the visible light source, and an infrared light in a light of a light source which is transmitted through a globe is reflected by the reflector, is transmitted through the front lens and is distributed forward.
An infrared light irradiation region in a forward portion of a vehicle is photographed by a CCD camera having a sensitivity up to a near-infrared which is provided in a front part of an automobile, is processed by an image processing apparatus and is projected onto a monitor screen in a vehicle compartment. A driver can confirm a person, a lane mark and an obstacle over the monitor screen projecting a field of view in the forward part of the vehicle at a great distance.
In the conventional infrared irradiation lamp, however, a halogen bulb to be a visible light source is surrounded by the infrared light transmission globe. Therefore, the inside of the globe is filled with heat generated from the bulb so that the inside of the globe has a high temperature. For this reason, there is a problem in that the halogen cycle of the halogen bulb does not function so that the lifetime of the bulb or the infrared light transmission globe is shortened, for example, blacking is generated to decrease an amount of a light or the infrared light transmission multilayer film of the globe is deteriorated to degrade an infrared ray cut characteristic.
Further, an infrared light transmission multilayer film cannot completely cut a visible light on the long-wavelength side of approximately 700 to 800 nm. Therefore, the lamp is seen to be turned on. For this reason, there is a possibility that the infrared irradiation lamp provided in the front part of an automobile might be erroneously recognized as a tail lamp or a stop lamp. Therefore, there is a problem in respect of safety.
Secondly, a halogen cycle does not function in a halogen bulb to be a visible light source. Consequently, there is a problem in that the lifetime of a light source or an infrared light transmission globe is shortened, for example, blacking is generated to decrease the amount of a light or the infrared light transmission multilayer film might be deteriorated to degrade an infrared ray cut characteristic.
The inventor made investigations for these causes. As a result, referring to the first problem, the red light component of the visible light which cannot completely be cut by the infrared light transmission globe (the visible light transmitted through the infrared light transmission globe) is guided to the whole reflector and a light reflected in a peripheral region of a light source in the reflector and emitted from the vicinity of the central part of a front lens has the highest energy (luminous flux density). Therefore, it has been confirmed that the vicinity of the central part of the front lens (the peripheral region of the light source in the reflector) is seen to emit a red light to be ring-shaped.
Referring to the second problem, moreover, the conventional infrared light transmission globe has a rear end thereof provided to abut on the reflector. Therefore, it has been confirmed that the inside of the infrared light transmission globe is filled with heat generated from a halogen bulb to be a visible light source, for example, and the lifetime of the light source or the infrared light transmission globe is thereby reduced, that is, blocking is generated to decrease the amount of the light and the infrared light transmission multilayer film is thermally degraded.
Therefore, the inventor supposed that the red light component of the visible light to be the cause of the lamp to be seen red is preferably diluted. Consequently, a clearance is provided between the rear end of the infrared light transmission globe and the reflector to directly guide a part of the light of the light source from the clearance to the peripheral region of the light source in the reflector. Thus, it has been confirmed that an advantage can be obtained in order to reduce a tone of red color for light emission of the lamp, and furthermore, the inside of the infrared light transmission globe is not filled with heat. Thus, the invention has been proposed.
The invention has been made based on the problems of the prior art and the knowledge of the inventor and has an object to provide an infrared irradiation lamp in which a clearance is provided between an infrared light transmission globe and a reflector so that the turn-on of a lamp is not erroneously recognized as a tail lamp or a stop lamp, and furthermore, the inside of the infrared light transmission globe is not filled with heat.
The invention has been made in consideration of the problems in the prior art and has an object to provide an infrared irradiation lamp in which the inside of a globe for infrared light formation is not filled with heat.
In order to achieve the object, a first aspect of the invention is directed to an infrared irradiation lamp for an automobile comprising a lamp housing formed by a lamp body and a front lens, a reflector provided in the lamp body, a light source provided ahead of the reflector in the lamp housing, and a cylindrical globe for infrared light formation which is provided to cover the light source and serves to shield a visible light and to transmit only an infrared light,
wherein the globe for infrared light formation has a rear end thereof provided apart from the reflector, and a light of the light source is directly guided from a clearance provided between the reflector and the rear end of the globe for infrared light formation to a peripheral region of the light source in the reflector.
The light distribution of the lamp includes the case in which a step for light distribution control is not provided on the front lens but the light is controlled and formed by only the reflector in addition to the case in which the light reflected by the reflector is controlled and formed at the step for light distribution control provided on the front lens. It is assumed that the front lens also includes the front lens having no step for light distribution control, that is, a so-called front cover. (Function)
The red light component of the visible light which cannot be completely cut by the globe for infrared light formation (the visible light transmitted through the globe for infrared light formation) is reflected by the whole reflector and is emitted from the front lens. A light reflected by the peripheral region of the light source in the reflector and emitted from the vicinity of the central part of the front lens corresponding to the peripheral region of the light source has the highest energy (luminous flux density). For this reason, conventionally, the vicinity of the central part of the front lens (the region corresponding to the peripheral region of the light source in the reflector) is seen to emit a light like a red ring. In the first aspect of the invention, a part of the light of the light source (the light of the light source which is not transmitted through the globe for infrared light formation) is directly guided from the clearance provided between the reflector and the rear end of the globe for infrared light formation toward the inside of the peripheral region of the light source in the reflector, and the light of the light source (white light) thus reflected is also emitted from the vicinity of the central part of the front lens corresponding to the peripheral region of the light source. Consequently, the luminous flux intensity of the red light component distributed forward from the vicinity of the central part of the front lens is reduced and the red light emitted from the lamp is diluted.
Moreover, an air convection is generated across the inside and outside of the globe for infrared light formation through the clearance provided between the reflector and the rear end of the globe for infrared light formation. Thus, the heat in the globe is radiated out of the globe.
A second aspect of the invention is directed to the infrared irradiation lamp according to the first aspect of the invention, wherein a shielding shade for shielding the light of the light source emitted from an opening on a front end side of the globe is provided ahead of the globe for infrared light formation, and a clearance is provided between the shielding shade and the globe for infrared light formation.
(Function)
The shielding shade provided ahead of the globe for infrared light formation shields the light of the light source emitted forward from the opening on the front end side of the globe, thereby blocking the generation of a glare light.
Moreover, the clearance is provided between the rear end of the globe for infrared light formation and the reflector, and furthermore, the clearance is provided between the shielding shade and the front end of the globe for infrared light formation (the front and rear ends of the globe are opened). Consequently, an air convection is easily generated across the inside and outside of the globe for infrared light formation. In addition, the air convection in the globe becomes active.
A third aspect of the invention is directed to the infrared irradiation lamp according to the first or second aspect of the invention, wherein an outer periphery of the rear end of the globe for infrared light formation is provided with an annular light shielding portion to be a part of a metallic holder for fixing and holding the globe for infrared light formation into the reflector or the shielding shade.
(Function)
A part of the red light component of the visible light transmitted through the globe for infrared light formation toward the peripheral region of the light source in the reflector is shielded by the annular light shielding portion provided in the globe for infrared light formation. Therefore, the total amount of the red light component guided to the peripheral region of the light source in the reflector is correspondingly decreased so that the red light component emitted from the region of the central part of the front lens is diluted still more.
Moreover, since the globe for infrared light formation is gripped by the annular light shielding portion to be a part of the metallic holder in a whole circumferential direction, the globe is fixed and held firmly without a looseness with respect to the reflector.
In order to achieve the object, a fourth aspect of the invention is directed to an infrared irradiation lamp for an automobile comprising a lamp housing formed by a lamp body and a front lens, a reflector provided in the lamp body, a bulb to be a light source inserted and attached into a bulb insertion attachment hole of the reflector and provided ahead of the reflector, and a cylindrical globe for infrared light formation which is provided to cover the bulb and serves to shield a visible light and to transmit only an infrared light,
wherein a metallic bulb holding member having a radiation fin extended to a back of the reflector is provided between the bulb insertion attachment hole and a mouth piece of the bulb.
The light distribution of the lamp includes the case in which a step for light distribution control is not provided on the front lens but the light is controlled and formed by only the reflector in addition to the case in which the light reflected by the reflector is controlled and formed at the step for light distribution control which is provided on the front lens. It is assumed that the front lens also includes the front lens having no step for light distribution control, that is, a so-called front cover.
The heat generated by turning on the bulb is transferred to the metallic bulb holding member provided between the bulb insertion attachment hole and the mouth piece of the bulb and is radiated from the radiation fin extended to the back of the reflector into a space (for example, the lamp housing) provided on the back of the reflector so that the inside of the globe for infrared light formation is not filled with the heat.
A fifth aspect of the invention is directed to the infrared irradiation lamp according to the first aspect of the invention, wherein a front end of the bulb holding member is extended to such a position as to face the vicinity of a light emitting portion of the bulb.
The heat generated by turning on the bulb is immediately transferred to the front end of the bulb holding member extended to such a position as to face the vicinity of the light emitting portion of the bulb and is radiated from the radiation fin extended to the back of the reflector into the space (for example, the lamp housing) provided on the back of the reflector so that the inside of the globe for infrared light formation can be prevented from being filled with the heat still more.
In particular, the bulb holding member includes a cylindrical portion which almost comes in close contact with the mouth piece of the bulb and the bulb insertion attachment hole, and the radiation fin extended to be plate-shaped (for example, disc-shaped) almost orthogonally from the rear end of the cylindrical portion. Consequently, it is possible to maintain a high airtightness in the bulb insertion attachment hole and a great heat radiating property to the space provided on the back of the reflector.
A sixth aspect of the invention is directed to the infrared irradiation lamp according to the first or second aspect of the invention, wherein the globe for infrared light formation has a rear end thereof provided apart from the reflector.
An air convection is generated across the inside and outside of the globe for infrared light formation through a clearance provided between the reflector and the rear end of the globe for infrared light formation. Thus, the heat in the globe is radiated out of the globe.
A seventh aspect of the invention is directed to the infrared irradiation lamp according to any of the first to third aspects of the invention, wherein a metallic shielding shade for shielding a direct light of a bulb which is emitted from an opening on a front end side of the globe is provided ahead of the globe for infrared light formation, and a clearance is provided between the shielding shade and the globe for infrared light formation.
The shielding shade shields the direct light of the bulb which is emitted from the opening on the front end of the globe for infrared light formation, thereby blocking the generation of a glare light. The shielding shade is formed of metal and there is no possibility that a thermal degradation might be caused.
An air convection is generated across the inside and outside of the globe for infrared light formation through the clearance provided between the shielding shade and the front end of the globe for infrared light formation so that the heat in the globe is radiated out of the globe. In particular, in the case in which a clearance is provided between the reflector and the rear end of the globe for infrared light formation, an air convection is easily generated across the inside and outside of the globe for infrared light formation. In addition, the air convection in the globe becomes active so that the heat radiating function of the air convection is promoted.
A eighth aspect of the invention is directed to the infrared irradiation lamp according to any of the first to fourth aspects of the invention, wherein the globe for infrared light formation is fixed to the reflector through a metallic globe holder provided in contact with an extended portion on a front end side of the bulb holding member.
The heat generated by turning on the bulb is transferred to the bulb holding member through the metallic globe holder for holding the globe for infrared light formation and is radiated from the radiation fin extended to the back of the reflector into the space (for example, the lamp housing) provided on the back of the reflector so that the inside of the globe for infrared light formation can be prevented from being filled with the heat still more.
Moreover, if (the leg of) the shielding shade and (the leg of) the globe holder are fastened and fixed together to the reflector with a screw, the heat of the shielding shade is also transferred to the bulb holding member through the globe holder and is thereby radiated from the radiation fin to the space provided on the back of the reflector. With such a structure that the globe holder comes in contact with the whole periphery of the cylindrical portion on the front end side of the bulb holding member, particularly, the globe for infrared light formation is fixed and held without a looseness with respect to the reflector, and furthermore, the area of a heat transfer path is increased so that heat radiating effects can be enhanced.
Furthermore, if the globe holder is constituted by a first globe holder for holding the globe and a second globe holder for backing up the first globe holder in engagement with (the cylindrical portion on the front end side of) the bulb holding member and a metallic elastic member such as a leaf spring or a coiled spring is provided between the globe holding the first globe holder and the second globe holder, the elastic member absorbs a vibration generated in the first globe holder (globe) and absorbs a thermal stress generated between the globe and the first globe holder.